Chlorine

1Identification

Name

Chlorine

IUPAC name

molecular chlorine

CAS number

7782-50-5

EC number

231-959-5

Molecular formula

Cl2

Molecular weight

70.9 g/mol

InChIKey

KZBUYRJDOAKODT-UHFFFAOYSA-N

SMILES

ClCl

PubChem CID

24526

Synonyms

Molecular chlorine, dichlorine, Bertholite, Chlorine gas, Chlorinum, Chloor, Chlore, Chlor, Cloro, Chlorine mol., Chlorine 35, UN 1017, Gas, Chlorine, Cl2 Gas

Recommended uses

• Chlorine is a commonly used household cleaner and disinfectant. It is widely used as an oxidizing agent in water treatment and chemical processes. It is also used in the bleaching process of wood pulp in pulp mills.
  EPA Hazardous Air Pollutants
• Used in water purification, paper manufacturing, and the synthesis of chlorinated hydrocarbons; [Levy, p. 409] Also used in shrink-proofing wool; [ACGIH]
  Haz-Map, Information on Hazardous Chemicals and Occupational Diseases
• Petroleum Production and Refining [Category: Industry] Pulp and Paper Processing [Category: Industry] Textiles (Fiber & Fabric Manufacturing) [Category: Industry] Using Disinfectants or Biocides [Category: Clean] Sewer and Wastewater Treatment [Category: Industry] Photographic Processing [Category: Other]
  Haz-Map, Information on Hazardous Chemicals and Occupational Diseases
• Processing aids not otherwise specified Monomers Semiconductor and photovoltaic agent Bleaching agent Opacifer Other Pigment Intermediate Oxidizing agent Brightener Cleaning agent Refrigerants Stabilizing agent Ion exchange agent Soil amendments (fertilizers)
  EPA Chemical Data Reporting (CDR)
• Bleaching agent Semiconductor and photovoltaic agent Other Intermediate Soil amendments (fertilizers) Refrigerants
  EPA Chemical Data Reporting (CDR)

Use categories: Chemical Classes -> Inorganic substances, Metals/Elements (the simplest forms of matter) · Food Additives -> BLEACHING_AGENT; FLOUR_TREATMENT_AGENT -> JECFA Functional Classes

Description

• At room temperature, chlorine is a yellow-green gas that is heavier than air and has a strong irritating odor. It can be converted to a liquid under pressure or cold temperatures. Chlorine is mainly used as bleach in the manufacture of paper and cloth and to make a wide variety of products.
  Agency for Toxic Substances and Disease Registry (ATSDR)
• Chlorine appears as a greenish yellow gas with a pungent suffocating odor. Toxic by inhalation. Slightly soluble in water. Liquefies at -35 °C and room pressure. Readily liquefied by pressure applied at room temperature. Contact with unconfined liquid can cause frostbite by evaporative cooling. Does not burn but, like oxygen, supports combustion. Long-term inhalation of low concentrations or short-term inhalation of high concentrations has ill effects. Vapors are much heavier than air and tend to settle in low areas. Contact CHEMTREC to activate chlorine response team 800-424-9300. Used to purify water, bleach wood pulp, and to make other chemicals.
  CAMEO Chemicals
• Dichlorine is a gas molecular entity and a diatomic chlorine. It has a role as a bleaching agent.
  ChEBI

2Hazard identification

Signal word

Danger

Pictograms

GHS03, GHS04, GHS06, GHS09

Classification source

Regulation (EC) No 1272/2008 of the European Parliament and of the Council

Precautionary statements

Other reported classifications

6 classification records exist across sources. Differences usually reflect purity, physical form or impurities.

NFPA 704 rating

• OX - Oxidizer: Materials that possess oxidizing properties.
  Occupational Safety and Health Administration (OSHA)

Health hazards

• Poisonous; may be fatal if inhaled. Contact may cause burns to skin and eyes. Bronchitis or chronic lung conditions. (EPA, 1998)
  CAMEO Chemicals
• · TOXIC and/or CORROSIVE; may be fatal if inhaled or absorbed through skin. · Fire will produce irritating, corrosive and/or toxic gases. · Contact with gas or liquefied gas may cause burns, severe injury and/or frostbite. · Runoff from fire control or dilution water may cause environmental contamination.
  Emergency Response Guidebook (ERG)

Fire hazards

• May ignite other combustible materials (wood, paper, oil, etc.). Mixture with fuels may cause explosion. Container may explode in heat of fire. Vapor explosion and poison hazard indoors, outdoors or in sewers. Hydrogen and chlorine mixtures (5-95%) are exploded by almost any form of energy (heat, sunlight, sparks, etc.). May combine with water or steam to produce toxic and corrosive fumes of hydrochloric acid. Emits highly toxic fumes when heated. Avoid plastics and rubber. Avoid heat and contact with hydrogen gas or powdered metals. (EPA, 1998)
  CAMEO Chemicals
• · Substance does not burn but will support combustion. · Vapors from liquefied gas are initially heavier than air and spread along ground. · These are strong oxidizers and will react vigorously or explosively with many materials including fuels. · May ignite combustibles (wood, paper, oil, clothing, etc.). · Some will react violently with air, moist air and/or water. · Cylinders exposed to fire may vent and release toxic and/or corrosive gas through pressure relief devices. · Containers may explode when heated. · Ruptured cylinders may rocket.
  Emergency Response Guidebook (ERG)
• Not combustible but enhances combustion of other substances. Many reactions may cause fire or explosion. Risk of fire and explosion. See Chemical Dangers.
  ILO-WHO International Chemical Safety Cards (ICSCs)

Hazards summary

• At room temperature, chlorine is a yellow-green gas that is heavier than air and has a strong irritating odor. It can be converted to a liquid under pressure or cold temperatures. Chlorine is mainly used as bleach in the manufacture of paper and cloth and to make a wide variety of products.
  Agency for Toxic Substances and Disease Registry (ATSDR)
• Chlorine is a commonly used household cleaner and disinfectant. Chlorine is a potent irritant to the eyes, the upper respiratory tract, and lungs. Chronic (long-term) exposure to chlorine gas in workers has resulted in respiratory effects, including eye and throat irritation and airflow obstruction. No information is available on the carcinogenic effects of chlorine in humans from inhalation exposure. A National Toxicology Program (NTP) study showed no evidence of carcinogenic activity in male rats or male and female mice, and equivocal evidence in female rats, from ingestion of chlorinated water. EPA has not classified chlorine for potential carcinogenicity.
  EPA Hazardous Air Pollutants

3Composition / information on ingredients

This page describes the pure substance. Commercial products may be solutions or mixtures. Check Section 3 of your supplier's SDS for concentrations and other ingredients.

4First-aid measures

• Warning: Effects may be delayed. Caution is advised. Chlorine is corrosive and may be converted to hydrochloric acid in the lungs. Signs and Symptoms of Acute Chlorine Exposure: Signs and symptoms of acute exposure to chlorine may include tachycardia (rapid heart rate), hypertension (high blood pressure) followed by hypotension (low blood pressure), and cardiovascular collapse. Pulmonary edema and pneumonia are often seen. The eyes, nose, throat, and chest may sting or burn following exposure to chlorine. Cough with bloody sputum, a feeling of suffocation, dizziness, agitation, anxiety, nausea, and vomiting are common. Dermal exposure may result in sweating, pain, irritation, and blisters.
  CAMEO Chemicals
• General First Aid: · Call 911 or emergency medical service. · Ensure that medical personnel are aware of the material(s) involved, take precautions to protect themselves and avoid contamination. · Move victim to fresh air if it can be done safely. · Administer oxygen if breathing is difficult. · If victim is not breathing: -- DO NOT perform mouth-to-mouth resuscitation; the victim may have ingested or inhaled the substance. -- If equipped and pulse detected, wash face and mouth, then give artificial respiration using a proper respiratory medical device (bag-valve mask, pocket mask equipped with a one-way valve or other device).
  Emergency Response Guidebook (ERG)
• (General first aid procedures) Eye: Frostbite - If eye tissue is frozen, seek medical attention immediately; if tissue is not frozen, immediately and thoroughly flush the eyes with large amounts of water for at least 15 minutes, occasionally lifting the lower and upper eyelids. If irritation, pain, swelling, lacrimation, or photophobia persist, get medical attention as soon as possible. Skin: Frostbite - Compressed gases may create low temperatures when they expand rapidly. Leaks and uses that allow rapid expansion may cause a frostbite hazard. Wear appropriate personal protective clothing to prevent the skin from becoming frozen. Breathing: Respiratory support
  The National Institute for Occupational Safety and Health (NIOSH)

Symptoms of exposure

• Cough. Sore throat. Shortness of breath. Wheezing. Laboured breathing. Symptoms may be delayed.
  ILO-WHO International Chemical Safety Cards (ICSCs)
• ON CONTACT WITH LIQUID: FROSTBITE. Redness. Burning sensation. Pain. Skin burns.
  ILO-WHO International Chemical Safety Cards (ICSCs)
• Watering of the eyes. Redness. Pain. Burns.
  ILO-WHO International Chemical Safety Cards (ICSCs)

5Fire-fighting measures

• Suitable extinguishing media: Use water spray, alcohol-resistant foam, dry chemical, or carbon dioxide.
  Hazardous Substances Data Bank (HSDB)
• Advice for firefighters: Wear self-contained breathing apparatus for firefighting if necessary.
  Hazardous Substances Data Bank (HSDB)
• Use water spray to cool unopened containers.
  Hazardous Substances Data Bank (HSDB)

6Accidental release measures

Isolation and evacuation

• Excerpt from ERG Guide 124 [Gases - Toxic and/or Corrosive - Oxidizing]: IMMEDIATE PRECAUTIONARY MEASURE: Isolate spill or leak area for at least 100 meters (330 feet) in all directions. SPILL: See ERG Tables 1 and 3 - Initial Isolation and Protective Action Distances on the UN/NA 1017 datasheet. FIRE: If tank, rail tank car or highway tank is involved in a fire, ISOLATE for 800 meters (1/2 mile) in all directions; also, consider initial evacuation for 800 meters (1/2 mile) in all directions. (ERG, 2024)
  CAMEO Chemicals
• Immediate precautionary measure · Isolate spill or leak area for at least 100 meters (330 feet) in all directions. Spill · See Table 1 - Initial Isolation and Protective Action Distances. Fire · If tank, rail tank car or highway tank is involved in a fire, ISOLATE for 800 meters (1/2 mile) in all directions; also, consider initial evacuation for 800 meters (1/2 mile) in all directions.
  Emergency Response Guidebook (ERG)

Spill cleanup

• Evacuate danger area! Consult an expert! Personal protection: gas-tight chemical protection suit including self-contained breathing apparatus. Ventilation. Shut off cylinder if possible. Isolate the area until the gas has dispersed. NEVER direct water jet on liquid. Remove gas with fine water spray. Do NOT let this chemical enter the environment.
  ILO-WHO International Chemical Safety Cards (ICSCs)
• ACCIDENTAL RELEASE MEASURES: Personal precautions, protective equipment and emergency procedures: Wear respiratory protection. Avoid breathing vapors, mist or gas. Ensure adequate ventilation. Evacuate personnel to safe areas. Environmental precautions: Prevent further leakage or spillage if safe to do so. Do not let product enter drains. Discharge into the environment must be avoided. Methods and materials for containment and cleaning up: Contain spillage, and then collect with an electrically protected vacuum cleaner or by wet-brushing and place in container for disposal according to local regulations.
  Hazardous Substances Data Bank (HSDB)
• Neutralizing agents: calcium carbonate, hydroxide, or oxide, adventitious crustacean shells, sodium hydroxide or carbonate, limestone, or dolomite. Reducing agents: calcium sulfite hemihydrate, lignite filtrate, or cellulose sulfite liquor from wood pulping. Sorbents: activated carbon, polyurethane, polyolefin and Dowex 1. Sodium thiosulfate should be used for dechlorination.
  Hazardous Substances Data Bank (HSDB)
• Construct barriers to contain spill or divert to impermeable surfaces. Immobilize spill with recommended materials. Remove material with dredges, pumps or vacuum equipment. Absorb small amounts of spill with sawdust, sand, or synthetic sorbents, shovel into containers with covers.
  Hazardous Substances Data Bank (HSDB)

7Handling and storage

• Fireproof if in building. Provision to contain effluent from fire extinguishing. Separated from food and feedstuffs. See Chemical Dangers. Cool. Dry. Keep in a well-ventilated room. Store in an area without drain or sewer access.
  ILO-WHO International Chemical Safety Cards (ICSCs)
• Keep container tightly closed in a dry and well-ventilated place. Contents under pressure. Storage class (TRGS 510): Gases.
  Hazardous Substances Data Bank (HSDB)
• Store in a cool, dry, well-ventilated location. Separate from combustible, organic, or easily oxidizable materials. Isolate from acetylene, ammonia, hydrogen, hydrocarbons, ether, turpentine, and finely divided metals. Outside or detached storage is preferred.
  Hazardous Substances Data Bank (HSDB)
• Permanent storage of chlorine is generally not recommended. However, at chlorine producing plants and barge shipping terminals, chlorine storage is an obvious necessity. Moderate amt may be handled in high strength tanks as a liquefied gas under pressure. The max amt that is considered safe under these conditions is about 450 tons. For larger quantities, low temp storage at atmosphere pressure is preferred in the interest of safety as well as economy. Chlorine gas evaporating from the low temp storage tank is reliquefied by a small refrigeration unit and recycled to storage.
  Hazardous Substances Data Bank (HSDB)

8Exposure controls / personal protection

Personal protective equipment

• Excerpt from NIOSH Pocket Guide for Chlorine: Skin: FROSTBITE - Compressed gases may create low temperatures when they expand rapidly. Leaks and uses that allow rapid expansion may cause a frostbite hazard. Wear appropriate personal protective clothing to prevent the skin from becoming frozen. Eyes: FROSTBITE - Wear appropriate eye protection to prevent eye contact with the liquid that could result in burns or tissue damage from frostbite. Wash skin: No recommendation is made specifying the need for washing the substance from the skin (either immediately or at the end of the work shift).
  CAMEO Chemicals
• Eye/face protection: Face shield and safety glasses. Use equipment for eye protection tested and approved under appropriate government standards such as NIOSH (US) or EN 166(EU).
  Hazardous Substances Data Bank (HSDB)
• Skin protection: Handle with gloves.
  Hazardous Substances Data Bank (HSDB)
• Body Protection: Complete suit protecting against chemicals. The type of protective equipment must be selected according to the concentration and amount of the dangerous substance at the specific workplace.
  Hazardous Substances Data Bank (HSDB)

Respirator recommendations

• NIOSH Up to 5 ppm: (APF = 10) Any chemical cartridge respirator with cartridge(s) providing protection against the compound of concern* (APF = 10) Any supplied-air respirator* Up to 10 ppm: (APF = 25) Any supplied-air respirator operated in a continuous-flow mode* (APF = 25) Any powered, air-purifying respirator with cartridge(s) providing protection against the compound of concern* (APF = 50) Any chemical cartridge respirator with a full facepiece and cartridge(s) providing protection against the compound of concern (APF = 50) Any air-purifying, full-facepiece respirator (gas mask) with a chin-style, front- or back-mounted canister providing protection against the compound of concern (APF =…
  The National Institute for Occupational Safety and Health (NIOSH)

9Physical and chemical properties

10Stability and reactivity

Reactivity

• CHLORINE reacts explosively with or supports the burning of numerous common materials. Ignites steel at 100 °C in the presence of soot, rust, carbon, or other catalysts. Ignites dry steel wool at 50 °C. Reacts as either a liquid or gas with alcohols (explosion), molten aluminum (explosion), silane (explosion), bromine pentafluoride, carbon disulfide (explosion catalyzed by iron), 1-chloro-2-propyne (excess chlorine causes an explosion), dibutyl phthalate (explosion at 118 °C), diethyl ether (ignition), diethyl zinc (ignition), glycerol (explosion at 70-80 °C), methane over yellow mercury oxide (explosion), acetylene (explosion initiated by sunlight or heating), ethylene over mercury, mercury…
  CAMEO Chemicals
• Water dissolves about twice its volume of chlorine gas, forming a mixture of hydrochloric acid and hypochlorous acids. Will be corrosive due to acidity and oxidizing potential.
  CAMEO Chemicals

Incompatible materials and hazardous reactions

• Incompatible materials: Alcohols.
  Hazardous Substances Data Bank (HSDB)
• Antimony burns spontaneously in gaseous chlorine; with liquid chlorine, antimony ignites at 33 °C.
  Hazardous Substances Data Bank (HSDB)
• Arsenic burns spontaneously in gaseous chlorine; with liquid chlorine, arsenic ignites at 33 °C.
  Hazardous Substances Data Bank (HSDB)

Chemical stability

• Stable under recommended storage conditions.
  Hazardous Substances Data Bank (HSDB)

11Toxicological information

Target organs

• Dermal (Skin), Gastrointestinal (Stomach and Intestines, part of the digestive system), Respiratory (From the Nose to the Lungs)
  Agency for Toxic Substances and Disease Registry (ATSDR)
• Eyes, skin, respiratory system
  The National Institute for Occupational Safety and Health (NIOSH)

Short-term exposure effects

• Lachrymation. The substance is corrosive to the eyes, skin and respiratory tract. Rapid evaporation of the liquid may cause frostbite. Inhalation may cause asthma-like reactions. Inhalation may cause pneumonitis. Inhalation may cause lung oedema, but only after initial corrosive effects on eyes and/or airways have become manifest. Exposure could cause death.
  ILO-WHO International Chemical Safety Cards (ICSCs)

Long-term exposure effects

• The substance may have effects on the respiratory tract and lungs. This may result in chronic inflammation and impaired functions. The substance may have effects on the teeth. This may result in erosion.
  ILO-WHO International Chemical Safety Cards (ICSCs)

12Ecological information

Not available in the public sources we compile. Check Section 12 of the supplier's SDS.

13Disposal considerations

• SRP: Recycle any unused portion of the material for its approved use or return it to the manufacturer or supplier. Ultimate disposal of the chemical must consider: the material's impact on air quality; potential migration in air, soil or water; effects on animal, aquatic and plant life; and conformance with environmental and public health regulations. If it is possible or reasonable use an alternative chemical product with less inherent propensity for occupational harm/injury/toxicity or environmental contamination.
  Hazardous Substances Data Bank (HSDB)
• SRP: Wastewater from contaminant suppression, cleaning of protective clothing/equipment, or contaminated sites should be contained and evaluated for subject chemical or decomposition product concentrations. Concentrations shall be lower than applicable environmental discharge or disposal criteria. Alternatively, pretreatment and/or discharge to a permitted wastewater treatment facility is acceptable only after review by the governing authority and assurance that "pass through" violations will not occur. Due consideration shall be given to remediation worker exposure (inhalation, dermal and ingestion) as well as fate during treatment, transfer and disposal.
  Hazardous Substances Data Bank (HSDB)
• Product: Contact a licensed professional waste disposal service to dispose of this material. Burn in a chemical incinerator equipped with an afterburner and scrubber but exert extra care in igniting as this material is highly flammable. Offer surplus and non-recyclable solutions to a licensed disposal company; Contaminated packaging: Dispose of as unused product.
  Hazardous Substances Data Bank (HSDB)

14Transport information

UN number: UN 1017

Shipping name

• UN 1017; Chlorine
  Hazardous Substances Data Bank (HSDB)
• IMO 2.3; Chlorine
  Hazardous Substances Data Bank (HSDB)

DOT hazard class

• Chlorine
  US Code of Federal Regulations, Hazardous Materials, 49 CFR Part 172
• Marine pollutant
  US Code of Federal Regulations, Hazardous Materials, 49 CFR Part 172
• UN1017
  US Code of Federal Regulations, Hazardous Materials, 49 CFR Part 172

DOT label

• Poison Gas Oxidizer Corrosive
  CAMEO Chemicals

UN classification

• UN Hazard Class: 2.3; UN Subsidiary Risks: 5.1 and 8
  ILO-WHO International Chemical Safety Cards (ICSCs)

Emergency Response Guidebook

• 1017 124
  Emergency Response Guidebook (ERG)

How DOT hazard classes work →

15Regulatory information

• Listed as a hazardous air pollutant (HAP) generally known or suspected to cause serious health problems. The Clean Air Act, as amended in 1990, directs EPA to set standards requiring major sources to sharply reduce routine emissions of toxic pollutants. EPA is required to establish and phase in specific performance based standards for all air emission sources that emit one or more of the listed pollutants. Chlorine is included on this list.
  Hazardous Substances Data Bank (HSDB)
• Chlorine gas is exempted from the requirement of a tolerance when used preharvest or postharvest in solution on all raw agricultural commodities.
  Hazardous Substances Data Bank (HSDB)
• Based on the reviews of the generic data for the active ingredient chlorine, the Agency has sufficient information on the health effects of chlorine and on its potential for causing adverse effects in fish and wildlife and the environment. The Agency has determined that chlorine products, labeled and used as specified in this Reregistration Eligibility Decision, will not pose unreasonable risks or adverse effects to humans or the environment if products are labeled and applied according to the requirements specified in Section V. Therefore, the Agency concludes that products containing chlorine for all uses are eligible for reregistration.
  Hazardous Substances Data Bank (HSDB)
• Chlorine is designated as a hazardous substance under section 311(b)(2)(A) of the Federal Water Pollution Control Act and further regulated by the Clean Water Act Amendments of 1977 and 1978. These regulations apply to discharges of this substance. This designation includes any isomers and hydrates, as well as any solutions and mixtures containing this substance.
  Hazardous Substances Data Bank (HSDB)
• The ambient water quality criterion for chlorine based on a daily water consumption of 2 L to protect human health is recommended to be 10.0 mg/L.
  Hazardous Substances Data Bank (HSDB)
• Persons in charge of vessels or facilities are required to notify the National Response Center (NRC) immediately, when there is a release of this designated hazardous substance, in an amount equal to or greater than its reportable quantity of 10 lb or 4.54 kg. The toll free number of the NRC is (800) 424-8802. The rule for determining when notification is required is stated in 40 CFR 302.4 (section IV. D.3.b).
  Hazardous Substances Data Bank (HSDB)
• D002; A solid waste containing chlorine may become characterized as a hazardous waste when subjected to testing for corrosivity as stipulated in 40 CFR 261.22, and if so characterized, must be managed as a hazardous waste.
  Hazardous Substances Data Bank (HSDB)

Overview of SDS regulations (OSHA HazCom, WHMIS, REACH/CLP) →

16Other information

Compiled from PubChem CID 24526 and the sources it aggregates (attributed inline). Data retrieved 2026-10-12. This summary describes the pure substance and is not a supplier SDS.